What is OHS? | ResMed
What is OHS?

What is OHS?

OHS is defined as chronic daytime hypercapnia (PaCOof over 45 mmHg) in obese patients (those with a BMI of > 30kg/m2) after ruling out any other causes of hypoventilation.1

As a result of poor breathing, those with OHS suffer from excess carbon dioxide (hypoventilation) and insufficient oxygen in their blood (hypoxemia).

OHS symptoms include:

  •  Dyspnoea2
  •  Excessive daytime sleepiness (EDS) 2
  •  Morning headache2
  •  Depression                                                                                                                                                                                                                                                               

As many as 90% of patients with OHS also suffer from obstructive sleep apnoea (OSA).


  1. Olson AL, Zwillich C. The obesity hypoventilation syndrome. Am J Med. 2005 Sep 118(9): 948-56
  2. Mokhlesi B, Kryger MH, Grunstein RR. (2008) Assessment and management of patients with obesity hypoventilation syndrome. Proc Am Thorac Soc 5:218–225